Purpose: The cause of Paget’s disease, osteitis deformans, defined by increased bone resorption followed by excessive attempts at repair, remains unclear. The current hypothesis is that bone is slowly infected by paramyxovirus in genetically predisposed patients. We report the case of a patient with monostotic Paget’s disease of the pelvis which was transferred to the homolateral distal femur after total hip arthroplasty.

Case report: A 66-year-old man with Paget’s disease of the hemi-pelvis developed pagetic hip deformation requiring a total hip arthroplasty performed in 1993. A Charnley-Kerboull cemented prosthesis was implanted. The medullary canal was plugged with fragments of cancellous bone harvested from the acetabulum (drill holes required to achieve rotatory stability of the acetabulum). One year later, an asymptomatic osteolytic lesion of the distal femur was identified at the level of the medullary plug. Hip function remained excellent despite extension to the distal and proximal femur. All inflammatory parameters were normal and the femoral component was not loosened. 99m-technetium scintigraphy revealed strong uptake in the pelvis but also in the distal femur under the femoral stem. Isolated femoral stem revision was performed in 1996 as a preventive measure against stress fracture. Pathology analysis of surgical specimens identified Paget’s disease (osteoclast hyperactivity, mosaic aspect of the osteoblasts. After femoral revision with a long stem and medical treatment with biphosphonates, the osteolytic lesion disappeared progressively, taking on the classical sclerous sequelar aspect of osteitis deformans. The disease remained quiescent six years after revision. Hip function remained excellent at last follow-up.

Discussion and conclusion: This is the first report of this type of complication after total hip arthroplasty. This observation that Paget’s disease can be transferred via a autologous cancellous bone graft is in favour of the viral hypothesis, suggesting osteoclastic infection by contiguity. This complication has never been observed with frozen or radiated allograft material although such material may have been harvested from pathological bone, notably with Paget’s disease